Qbus Backplanes

From: Tothwolf <tothwolf_at_concentric.net>
Date: Fri Jun 6 14:30:03 2003

On Thu, 5 Jun 2003, Peter Turnbull wrote:
> On Jun 5, 16:19, Tothwolf wrote:
>
> > Since we are on the subject of VAXen...
> >
> > What would be the most likely problem with a BA123 MicroVAX II that
> > powers up, but sometimes totally locks up during the diagnostics? (I'm
> > not even sure it can boot, as some of the RD53s sound a little sick.)
> > I've pretty much eliminated the boards as the cause, and the only
> > things left are the backplane and power supply. It does have those
> > older power supply to backplane wiring harness cables, which I guess I
> > need to replace before I put many boards in the card cage.
>
> Could be voltage drop between PSU and backplane, resulting in low
> voltage on the cards. Part of the problem with the harness (which was
> discussed here some months ago, in a different context) is that parts go
> high-resistance. Check the voltage (especially the +5V) on one of the
> cards.

I checked the voltages on the drive harnesses, and +5VDC and +12VDC seemed
to be within the normal variance. I'll see if I can't check +5VDC on some
of the boards too. I guess if that checks out ok, I'm to where I started,
thinking that there may be noise on +5VDC and/or +12VDC. Has anyone else
had similar problems with the BA123 power supply?

-Toth
Received on Fri Jun 06 2003 - 14:30:03 BST